This invention relates to an improved wire wrapping machine and more particularly to a control means for a wire wrapping machine which is so constructed that a spindle for wrapping a lead wire of the wire wrapping machine is automatically and reversely rotted to stop at the fixed position in relation to a sleeve supporting the spindle therein.
Recently, in order to save the assembly works of the electronic circuit parts, a so-called "wire wrapping" is generally used in which a stripped portion of the lead wire is wrapped tightly without soldering around a metal terminal, which is protruded from the base circuit plate, of a circuit element such as electrolytic condenser or resistor.
A working instrument for effecting the wire wrapping operation is generally called as a wire wrapping machine which comprises a lead wire wrapping spindle rotatable by a driving power source of an electric motor or an air motor and an outer sheath sleeve for supporting rotatably the spindle therein. The spindle 10, as is shown in FIG. 1, is provided at its center with a hole 14 of a predetermined depth for receiving a bar terminal 12 of a circuit element 11 and formed longitudinally with a slot 16 on its periphery for holding the lead wire. This spindle 10 is connected through a clutch means as hereinafter described to the motor accommodated in the wrapping machine. The spindle 10 is contained in an outer sleeve 22 having a somewhat larger inner diameter than that of the spindle and being fixed to the machine.
In the wrapping operation of the lead wire, the stripped portion of the lead wire 24 such as the vinyl wrapped copper wire is inserted into the slot 16, on this step since the spindle 10 is enclosed in the fixed sleeve 22, the lead wire 24 is held by the slot 16 and an inner circumferential wall of the sleeve 22 without slipping out, then the bar terminal 12 of the circuit element 11 protruding vertically from the circuit base plate 26 is vertically inserted into the central hole 14 of the spindle 10 which is in turn constrained to rotate for the predetermined period by holding the wrapping machine so that the stripped portion of the lead wire 24 is tightly wrapped around the bar terminal 12 as shown in FIG. 2 to obtain a complete conductive connection. At the open end of the sleeve 22 there is provided a recess 28 for enabling the wrapping of the lead wire from the base of the bar terminal. To achieve a rapid and continuous wrapping of the lead wire the necessity arises of providing a mechanism in which the spindle 10 when the motor is stopped is returned to a specified position in the sleeve 22 to align an open end of the slot 16 with the recess 28 as shown in FIG. 3.
For this purpose, in the conventional wrapping machine a ratchet mechanism (not shown) is incorporated so that when the operation of the spindle 10 is stopped after completion of wrapping of the lead wire 24 the spindle 10 is turned reversely under the function of the spring for engagement with the ratchet to stay stationarily at the specific position in the sleeve 22. Since, however, the return elasticity of the spindle when stopped is not sufficient enough and the spindle in a direct connection with the motor receives an excessive load and accordingly the reverse rotation by the elasticity can not be obtained. To resolve this problem, in the conventional wrapping machine a clutch means is arranged between the spindle and the motor driving shaft to release the connection therebetween for decreasing the resistance load against the spindle. However, inevitable use of the clutch means will result in increasment of the weight of the machine per se and the cost for manufacturing the machine. Furthermore, when the ac motor is used as a power source, there are such disadvantages that the change of rotation is difficult with much noise while when a compressed air is applied as a power source, a high exhaust noise is caused with use of a separate compressor.
After intensive studies of the above problem, the inventor has employed a dc motor which is conveniently reversible by merely changing the polarity to apply an inverse voltage thereto for a short period after cessation of the motor with completion of the wire wrapping thereby to turn the motor reversely. The reversely rotating spindle is enganed with a ratchet to stop at a determined position in relation to the outer sleeve. By this arrangement, the clutch means used in the conventional machine to release a connection between the spindle and the motor becomes unnecessary.
As a substantial manner for applying an inverse voltage to the motor for a short period, provision is made of a control means in which a first rectifying circuit and a second rectifying circuit are arranged and the dc motor is connected to the first rectifying circuit and a chargeable and dischargeable condensor of the great capacity is connected to a motor circuit in parallel so that the condenser is charged during the working operation of the motor and after completion of the wire wrapping operation the current supply from the first rectifying circuit to the motor is interrupted to shortcircuit the motor energizing circuit for passing a short current therethrough to interrupt the operation of the motor while commencing discharge of the condenser so that the discharge voltage energized a relay through an amplifying circuit thereby to switch the relay contact cooperative to the relay and inserted in series between the motor and the first rectifying circuit and the inverse current generated by the second rectifying circuit is supplied to the motor energizing circuit for the discharging period determined by the capacity of the condenser and the discharge resistance.
A general object of the present invention is to provide a control means for the wire wrapping machine comprising a lead wire wrapping spindle and an outer fixed sleeve for rotatably supporting the spindle in which after completion of the wire wrapping operation an inverse current is supplied to a motor for the short period to allow the spindle to rotate reversely so that a slot provided in the spindle always comes to a position in alignment with a recess provided in the outer sleeve. SUMARRY OF THE INVENTION
A principal object of the invention is to provide a control means for the wire wrapping machine comprising a lead wire wrapping spindle, an outer sleeve for turnably supporting the spindle and a dc driving motor accommodated therein and connected to an output of a rectifying circuit for converting the polarity of the current supplied to the motor on completion of the wire wrapping operation to supply an inversed voltage to the motor for the short period allowing the motor to rotate reversely so that the spindle is positioned through a ratchet means at a predetermined position in relation to the outer sleeve.
The means for supplying the inverse current to the dc motor for a short period includes a first rectifying circuit and a second rectifying circuit and the dc motor is connected to the first rectifying circuit whereas a condenser is connected in parallel to the dc motor which is shortcircuitted by breaking the conductivity with the first rectifying circuit and the condenser is discharged to actuate the relay control circuit thereby to supply the inverse current of the second circuit to the dc motor. One of the input terminals of the dc motor is connected through a motor switch to a positive output of the first rectifying circuit and a negative output of the second rectifying circuit whereas the opposite input terminal is switchably connected through a relay contact of the relay control circuit to a negative output of the first rectifying circuit and a positive output of the second rectifying circuit. Further, the relay control circuit includes a relay which is energized by the discharging current of the condenser and a relay contact cooperative with said relay is inserted in series between the dc motor and the first rectifying circuit and connected switchably to the output of the opposite porality of the second rectifying circuit.
Another objects and advantages of the invention will become clear by the following detailed description.
The invention will now be described in greater detail with reference to the accompanying drawings in which: